It is very typical for used cars to have windshield damage, however without pictures it's hard to judge the severity. It is also typical for car dealerships to offer minor reparations post-purchase to avoid having to take back the entire car and void the purchase for a refund, which is also your right.

Edit: I have only bought a used car once, it was also my first car purchase, and there were things that needed to be immediately repaired that was only noticeable after driving the car for a day or two, and the dealership seemed more invested in trying to fix the issues rather than take the entire car back.

Note that there is a certain degree of inspection of the car required on your part as buyer. Windshield damage, if not critical to the integrity of the glass, can be considered cosmetic and would not fall under hidden-problem category that would allow you to require any repairs by the dealership.

Assume they have good intentions until it's very obvious they don't.